Nanoscale surface characterization of aqueous copper corrosion: Effects of immersion interval and orthophosphate concentration

Morphology changes for copper surfaces exposed to different water parameters were investigated at the nanoscale with atomic force microscopy (AFM), as influenced by changes in pH and the levels of orthophosphate ions. Synthetic water samples were designed to mimic physiological chemistries for drinking water, both with and without addition of orthophosphate over a pH range 6.5–9. Copper surfaces treated with orthophosphate as a corrosion inhibitor after 6 and 24 h were evaluated. Tapping mode AFM images revealed dosing of the water with 6 mg/L of orthophosphate was beneficial in retarding the growth of copper by-products. The chemical composition and oxidation state of the surface deposits were characterized with X-ray diffraction (XRD), near edge X-ray absorption fine structure (NEXAFS) spectroscopy and Fourier transform infrared spectroscopy (FTIR).